grahn



0. GRAHN.

I AUIOMATJC AND SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED MAR. 20. I917.

1,807,196. PatentedJune17, 1919.

' s SHEETS-SHEET 1.

Patented June 17', 1919.

3 SHEETS-SHEET Z 0. GRAHN.

'APPLICATION FILED MAR. 20. 1917.

AUTOMATIC AND SEMLAUTOMATIC TELEPHONE SYSTEM,

Lmw. WASHINGYDN. n c.

O. GRAHN.

AUTOMAHC AND SEMI- AUTOMATIC TELEPHONE SYSTEM. APPLICATION FILED MAR.20.1917.

' L BUFJ 96o Patented June 17, 1919. Q J SSHEETS-SHEET 3.

EE SATES OSCAR GRAHN, OF LONDON, ENGLAND, ASSIGNOR TO THE RELAYAUTOMATIC TELEPHONE COMPANY, LIMITED, OF LONDON, ENGLAND.

Specification of Letters Patent.

Patented June 17, 1919.

Application filed March 20, 1917. Serial No. 156,047.

To all whom it may concern:

Be it known that I, OSCAR GRAnN, a sub ject of the King of Sweden,residing at Marconi House, Strand, London, England, have invented newand useful Improvements in Automatic and Semi-Automatic TelephoneSystems, of which the following is a .the functions required indifferent kinds of connections.

For instance, in a connection between two subscribers of an automaticexchange, it may be required that only effective calls shall beregistered, that no registration shall be made for calls to certainsubscribers and that the connection shall be automatically released incase the called subscriber is engaged. In a connection between asubscriber of an automatic exchange and an operator of a manualexchange, it may be desired that the operator, when answering, shalltake charge of the connection and control the release of the junctionbetween the exchanges, and further that a clearing signal shall be givento the operator from the calling subscriber. When the call is fromamanual exchange to a subscriber of an automatic exchange, the operatorshall be given suitable supervisory signals such as clearing signal fromthe called subscriberand a flash signal when the called subscriber isengaged.

As seen from these conditions the problem is largely a matter ofproviding circuits in connection with inter ofiice junctions and trunksin automatic exchanges capable of transmitting different signals orcurrent combinations over the talking connection to effect certainoperations at the calling and the called end of the connection, and sodesigned that they work together properly in difi'erent kinds ofconnections.

According to the present invention, in order to utilize the two linebranches of the talking connection more efficiently for said purposes,two relays controlling metering, disconnecting and supervisory circuitsare associated with each trunk or junction and connected each to oneline branch, means being provided at the called end of the connection tooperate said relays separately or together. To be able to use saidrelays for disconnecting purposes, they preferably remain connected tothe line branches during the conversation, energized in a loop circuitextending over the line of the called subscriber or over a junction.Further features of the invention will be described in connection withthe accompanying drawings in which z- Figure 1 illustrates part of atalking connection with the principal circuits of a set of transmittingrelays according to this invention:

Fig. 2 shows the calling end of a talking connection in an automaticexchange in which the connections are established by means of relaysonly:

Fig. 3 shows the called end of atalking connection in an automaticexchange:

Fig. 4 shows the transmission circuits associated with the incoming endof a junction line connecting two automatic exchangs:

Fig. 5 shows the principal circuits associated with the incoming end ofa junction joining an automatic and a manual exchange or an automaticsubscriber with a manual board at the automatic exchange:

Fig. 6 shows the principal circuits at a manual exchange for calls to anautomatic exchange and Fig. 7 shows the transmission circuits associatedwith the incoming end of a junction connecting a manual and an automaticex change.

In Fig. 1, A, B, C, D, E, are a set of transmission relays associatedwith a trunk leading to the first group switching stage in an automaticexchange. A and B are two transmitting relays according to theinvention, connected each to one line branch of said trunk andcontrolling certain circuits 1, 2, 3. C, is an impulse relay, and D andE the ordinary guarding and change-over relays, which are slow torelease their armatures. The impulse relay C, upon energizing, cuts inthe guarding relay D, which then remains in operated position till theconnection is completed, as will be described below. During thetransmission the se lective impulses, relay E is maintained energized inknown manner so that relays A and B are disconnected from the trunk.

The relays A and B are operated from the called end of the connection bymeans of devices here represented by two keys AK and BK. By operatingkey BK after the completion of the connection, 0., after relay D hasdeenergized, relay B is retained while A deenergizes, closing a circuit1 which may be a meter circuit, or may be utilized for preparing themeter circuit, if the call is to be registered after the end of theconversation. By operating key AK at the end of the conversation, A isretained while B de energizes, completing a circuit 2 which may beutilized for clearing purposes. In case the called subscriber should beengaged, key BK is operated before the guarding relay D has deenergizedthereby completing a circuit 3 which is utilized for busy-back signaland busy-back release.

A local automatic connection will now be described with reference toFigs. 2 and 3. The calling subscriber S1 when lifting his receiver,completes a circuit 4% through a line relay LRl which causes apparatuscommon to a number of subscribers to test the trunks T1 available tosaid subscribers and to operate those connecting relays CR1 and CR2 bywhich the calling line L1 can be connected to an idle trunk. Theoperations that take place are in all respects similar to thosedescribed in the British Patent Specification No. 9840/1914, and neednot therefore be particularly described in this connection. The impulserelay C is now energized over the subscribers line and completes aretaining circuit 5 including said connecting relays CR1 and CR2 and acutoff relay CORl. The latter operates, opens circuit 4 and energizes anauxiliary relay ARl over (3. Relay C, upon operating, closes a circuit'7 through the guarding relay D and a circuit 8 through a selectorconnecting relay SCRl belonging to a first group selector (not shown)which may be common to a number of trunks T1 as described in the BritishPatent Specification No. 29,615 of 1913. Relay SCRl completes circuit 9which includes relays A and B and a selector impulse relay SIRl. Suchrelays energize, B closing a holding circuit 10 for re lay D.

The subscriber now sends the impulses corresponding to the first digitof the number required. Upon the first deenergization 01": C, relay E isenergized over 11, whereby the selector impulse relay SIRl is switchedover without interruption in a circuit 12 controlled by C. When Creenergizes, the secondary impulse circuit 12 is opened for the firsttime. During the sending of the impulses A and B are deenergized whilethe guarding relay D is kept energized over a circuit 13.

Relay D maintains the third wire circuits 5 and 8 over contact 2%. Afterthe selector has been set it automatically puts into operation a devicewhich selects and operates two connecting relays CR3 and CR4 by whichtrunk T1 is connected to an idle trunk T2 outgoing in the requireddirection to the next group switching stage or to the final switchingstage, the group selector being automatically disconnected by theoperation of relay CR3. The operation of the selector, which has nothingto do with the invention, may be similar to that described in saidSpecification No. 29,6l5-of 1913.

Supposing said trunk T2 is a trunk leading to the final switching stage,as shown in Fig. 3, a third wire retaining circuit let is now completedthrough relays CR3 and CR4 and aselector connecting relay S'CR2. Atabout the same moment relay E deenergizes closing circuit 15 throughrelays A and B and the impulse relay SIR2 of the final selector (notshown).

The subscriber now sends the second train of impulses corresponding tothe hundreds digit of the number wanted. The change-over relay Eenergizes on the first deenergization of C, cuts off A and B, whichagain de'energize, and completes the impulse circuit 16. The finalselector is set by two trains of impulses operating chiefly as describedin said specification 9840 of 1914:. After having been set, it causesthe energization of a set of connecting relays CR5, CR6 and CR7 by whichthe trunk T2 is connected with the line L2 of the wanted subscriber S2.The final selector is therefore disconnected and the retaining circuit14 is maintained through CR5. The latter completes another retainingcircuit 17 through CR6 and CR7 a discriminating relay M and thecut-o'l'l' relay COR2 of the called subscriber. A relay H is initiallyen :ergized in a circuit parallel to that energizing CR5, and isretained over 18. Relay COR-2 energizes AR2 which disconnects the linerelay LR-2. -Relay M energizes if the called subscriber-is an ordinarysubscriber. If the called subscriber is one to whom calls are free, saidrelay does not operate owing to a resistance being inserted in the thirdwire circuit of such subscriber, for instance, between relays COR2 andAR2. At first it may be assumed that M does operate so that the call maybe registered.

The subscriber is now rung automatically in ordinary way by means notshown here. In the ITIGiLDtlH'IG relay D, Fig. 2, deenergizes. as relaysA and B now remain deenergized. hen the subscriber lifts his receiver toanswer, a circuit 19 is closed through one winding of a relay K, Fig. 3,the line of the called subscriber and relay A, Fig.2. Relay K operates,locks itself in a retaining circuit 20 and opens said circuit 19. At thesame time it opens the circuit of H and closes a circuit 21, relay Hbeing slow-acting so as to maintain circuit 21 for a moment. Relay B,Fig. 2, energizes in said circuit and closes a circuit 22 through ameter relay G which is retained over 23. Belay B also completes acircuit 25 in which a disconnecting control relay F is energized. Thethird wire circuits 5 and 14 are now maintained over 26 and are thusunder the control of relay B.

Relay H, upon deenergizing, closes a loop circuit 27 through relays Aand B and the called subscribers line, whereby the connection is putinto condition for conversation.

If the called subscriber is the first to restore his receiver, relays Aand B deenergize but nothing further happens, as relay F and the thirdwire circuits 5 and 14 are n1aintained over 28, F, being slow to releaseits armature. When the calling subscriber re places his receiver, relayC denergizes and opens circuit of G which, however, being slow-acting,keeps its armature attracted for a short interval during which aresistance R1 in circuit 5 is short-circuited over 30, whereby thecalling subscribers meter (not shown) which is included in the thirdwire circuit 5, is operated in well-known manner. When G denergizes, theretaining circuits 5 and 14 hitherto maintained over 30 are opened andthe connection is released.

Should the calling subscriber be the first to replace his receiver,relay B is short-circuited over 31 and denergizes while relay A remainsenergized over 31. The meter is operated as before and the connection isre leased when G deenergizes.

If the call is'not to be registered, relay M Fig. 8, is not energizedand, consequently, circuit 21 is not closed and the meter relay Gremains denergized. When relay ll-I, Fig. 8, deenergizes, the loopcircuit 27 is closed as before. The connection is released Withoutmetering. when the calling subscriber replaces his receiver.

In case the called subscriber should be .engaged in the moment ofestablishing the connection, the connecting relays CR6 and CR7 cannot beoperated and a circuit 32 is therefore completed through a relay N whichoperates and energizes K, which looks itself as before. Relays K and Ncomplete circuit 21 through contact 33 of relay N, thereby causing amomentary energization of relay B, Fig. 2. At this moment, however, theslow-acting guarding relay D has not had suflicient time to denergizeand a circuit 34 is therefore completed through relay F which maintainsthe third-wire circuits 5 and 14 over the same path 34. When relay Hdenergizes, B deenergizes, the retaining circuits 5 and 14 are openedand the connection is severed up to the calling subscribers line. Thecalling subscriberscut-off relay CORl, on deenergizing, completes aretaining circuit 35 through relay ARl and the line L1. A transformer 36adapted to give a busy-back signal is then connected up to the line.WVhen the subscriber hears the busy-tone he replaces the receiver,thereby opening circuit 35.

The circuits for a connection between two subscribers belonging to twodifferent automatic exchanges are obtained by placing together Figs. 2,4 and 3 in the order mentioned. Circuit 14 of relay CR4, Fig. 2, is thenconnected directly to battery. The connecting operations are the same asbefore described. When connection is made with the junction line J1, acircuit 37 is closed through an impulse relay C, Fig. 4; and relay A,Fig. 2. Relay C energizes and closes a circuit 38 through a selectorconnecting relay SCR3 of a second group -selector and a circuit 39through the guarding relay D. Relay SCB3 completes loop circuit 40through relays A and B and the selector impulse relay S1133. D isretained over 41. A and B close a loop-circuit through relays A and B,Fig. 2, over 42, Fig. 4, and through relay C. The selector is nowoperated in the ordinary way, relay D" being retained and E energized inthe manner described in connection with Fig. 2. During the sending ofthe impulses A and B are deenergized but the loop circuit extending overthe junction and through relay C is maintained over 43. After the secondgroup selector has been set, the connecting relays CR8 and CR9 areoperated as before described and the connection is extended to the trunkT2, Fig. 3, and to a final selector which is operated to complete theconnection as previously described.

While the called subscriber is being rung, D, Fig. 4, deenergizes. Theloop circuit over the junction is therefore opened and circuit 37 isreestablished whereby B, Fig. 2, is allowed to deenergize. When thesubscriber answers, assuming that the call is to be registered, acircuit 21 is again established as before described, this time, however,through relay B Fig. 4. This results in the energization of thecorresponding relay B, Fig. 2, over 44. At the same time a relay U isenergized over 45 and retained in the third wire to preventdisconnection by the called subscriber at the end of the conversation.Relay B, Fig. 2, energizing, operates the meter relay G as before. WhenH, Fig. 3, denergizes, the loop-circuit 27 is estab lished throughrelays A and B and the called subscribers line L2. A and B complete theloop circuit 42 through relays A and B, the junction J1 and relay C.

lVhen the called subscriber replaces his receiver, A and B deenergize,but the loopcircuit of relays A and B is now maintained through C over apath 46 controlled by relay U and back contacts of A and B. \Vhen thecalling subscriber restores his receiver, relay B, Fig. 2, isshortcircuited over 31 to prepare the release by opening the path 26.The connection is released when G deenergizes after having secured theoperation of the meter in the manner described.

A connection between a subscriber of an automatic exchange and a cordcircuit at a manual exchange is illustrated by Figs. 2 and 5. WVhen thecalling subscriber is connected to the junction J2, a circuit 47 isestablished through relay A, Fig. 2, and a supervisory relay V whichcloses a lamp circuit 48. The operator, seeing the lamp glowing,depresses the speaking key (not shown) ascertains the number wanted andinserts the plug P in the corresponding jack. Relay W operates, shuntsthe lamp and coinpletes at contact 49 the loop circuit through relays Aand B and the junction J2. Relay B, energizing, operates relay F andcompletes the path 26 over which the connection is now maintained underthe control of the operator.

At the end of the conversation, when the calling subscriber replaces hisreceiver, relay V, Fig. 5, is short-circuited over 31, and ondecnergizing removes the shunt across the supervisory lamp. Relay Bremains energized over the corresponding line branch thus maintainingthe connection. The operator, seeing the lamp glowing, depresses a meterkey MK, if the call is to be registered, thereby short-eircuiting relayA which, on denergizing, operates the meter relay G. The meter isimmediately operated over 30. To release the connection the operatorwithdraws the plug, thereby opening contact 19 of relay W and causingrelay B to deenergize. Belay B opens the path 26 and thereby the thirdwire retaining circuits 5 and l l.

Figs. 6, 7 and 3, placed together in the order mentioned, show aconnection between a cord circuit at a manual exchange and a subscriberof an automatic exchange. The junction J3 has associated with it animpulse sender key SK, by means of which an impulse sender of any knowntype can be connected to the line, and at the automatic exchange, Fig.7, a set of transmission rclays A, B C D and E controlling circuits insubstantially the same manner as the relay set shown in Fig. 4. Toestablish a connection the operator inserts plug P2 in the jack of anidle junction J3 and pulls key SK to connect up the impulse sender. Acircuit 50 is then closed through one line branch and relay C, Fig. 7.The latter energizes and operates a selector connecting relay SOFA. Aloop circuit is then completed as in Fi 4:, through relays A, B and theselector impulse relay SIRt. A" and B operate and close a loop circuit51 0 and the other line branch of the junction and openscircuit 52. Thesupervisory relay SR1 energizes in circuit 53 and short-circuits thelamp SL1, whereby the operator is informed that the called subscriberhas answered. When relay H, Fig. 3, deenergizes, the loop circuit 27 isclosed through relay A and B. The latter close in turn loopcircuit 51through relay C and the cord circuit, the supervisory lamp thusremaining short-circuited. When the called subscriber replaces hisreceiver, A and B deenergize, open the loop circuit 51 and close circuit52. Lamp SL1 glows, indicating that the called subscriber has cleared.Upon withdrawing plug P2 circuit 52 is opened, 0 dcenergizes and theconnection is released.

In case the called subscriber should be engaged, relay B Fig. 7 isenergized over 21, Fig. 3, before relay D has de'e'nergized and acircuit 541 is therefore established in which a busy-flash relay Q isenergized. The latter locks itself over 55 and completes a circuit 56,including an interrupter I and extending over one line branch throughthe supervisory relay SR1. The lamp SL1 is thereby flashed informing theoperator that the called subscriber is busy. Meanwhile relay C is keptenergized over 57 to maintain the connection. l/Vhen relay H, Fig. 3,deenergizes, relay B deenergizes, relay 0" being then maintainedenergized first over 58 and then, after D has denergized, over 52. Theconnection is released as before by withdrawing the plug P2.

lVhat I claim is 1. In a telephone system, two relays each connected toa different line branch of a talking connection, means associated with acalled junction for operating either of said relays over the talkingconnection and means for completing a loop-circuit through said relaysover the called subscribers talk ing connection.

2. In a telephone system, a talking connection including a two-wirejunction line, two relays each connected to a different line branch ofsaid junctionat one end thereof, means directly associated with theother end of said junction for operating either of said relays, andmeans. for completmg a loop circuit through said relays over saidjunction.

3. In a telephone system, a talking connection extending between twoexchanges connected by a two-wire junction line,two relays eachconnected to a different line branch of said junction at the outgoingend thereof, means associated with the junction at the distant exchangefor operating either of said relays, and means for completing a loopcircuit through said relays over said junction.

4:. In a telephone system, a talking connection involving connectingmeans at a manual board, two relays each connected to a difl'erent linebranch of the talking connection at the calling end thereof, means atthe manual board for operating either of said relays and means forcompleting a loop circuit through said relays over the talkingconnection.

5. In a telephone system, a talking connection involving connectingmeans at a manual board, two relays each connected to a different linebranch of the talking connection at the calling end thereof, means atthe manual board for operating either of said relays, a loop circuitincluding said relays and the two line branches, manually operated meansfor opening said loop circuit, a disconnecting circuit controlled bysaid relays and means for disconnecting the talking circuit by openingthe loop circuit.

6. In a telephone system, a talking connection involving connectingmeans at a manual board, two relays each connected to a different linebranch of the talking connection at the calling end thereof, means atthe manual board for controlling said relays and means controlled bysaid relays and operated from the manual board to transfer the controlof the disconnection into the hands of the manual operator.

7. In a telephone system, a t.lking con nection involving connectingmeans at a manual board, two relays each connected to a different linebranch of the talking connection at the calling end thereof, means atthe manual board for controlling said relays, means controlled by saidrelays and operated from the manual board to transfer the control of thedisconnection into the hands of the manual operator and means foroperating said relays from the side of the calling subscriber so as toeffect the disconnection of the talking circuit when not extendedthrough a manual board.

8. In a telephone system, a talking connection involving connecting andsupervisory means at a manual board, two relays each connected to adifi'erent line branch of the talking connection between the manualboard and the called party, means for con trolling said relays from thecalled end of the connection and supervisory circuits controlled by saidrelays.

9. In a telephone system, a talking connection involving connecting andsupervisory means at a manual board, two relays each connected to adifferent line branch of the talking connection between the manual boardand the called party, means for con trolling said rehys from the calledend of the connection, means for operating a busy flash signal throughsaid relays and means for operating a clearing signal through saidrelays.

10. In a telephone system a talking con nection extending between twoexchanges connected by a two-wire junction, manually operated means atthe first exchange for extending the connection to the second exchange,automatic means for extending the connection in the second exchange, tworelays each connected toa different line branch of said junction at theincoming end thereof, means for controlling said relays from the calledend of the connection and supervisory signals at the first exchangecontrolled through said relays.

11. In a telephone system, a talking connection extending between twoexchanges connected by a two-wire junction, two relays each connected toa different line branch of said junction at the outgoing end thereof,two other relays each connected to a difi'erent line branch of saidjunction at the incoming end thereof, means for operating either of thetwo relays last mentioned from the called end of the talking connectionand means for operating either of the two relays first mentioned throughthe said other relays.

OSCAR GRAHN.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. O.

